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Chapter 3

Lecture 1 / Chapter 3

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McMaster University
Life Sciences
Brett Beston

Chapter 3Thursday September 15 2011436 PMImmediate causation is proximate causationUltimate causation is when a trait has formed due to evolutionIn proximate causation we answer questions like Whatand HowProximateUltimateBehaviorIn proximate causationwe are working with factors that are affecting the organism here and nowwithin its lifespan no history or future is consideredExample male aggression has been selected for scavenging ultimate while it is also selected for mate securing during mating season proximateProximate analysis will help us understand howevolution has helped shape human aggressionGeoff Hill worked on house finches carpodacus mexicanuusHe started his experiment knowing that the coloration of the birds feather is due to carotenoidcolor pigments ingested by birds Meaning they completely rely on their diet for their colorationWhich meant that coloration of their plumage was due to Development Differences in what the males ate as they maturedThis experiment was based on female birdsOne set of female birds were fed a normal apple and the other set were fedcarotenoid The birds fed the carotenoid turned a brighter plumage whereas the birds fed the normal apple stayed the same This arose 2 questionsWhat causes the plumage color to change for the femalesbetween populations1What causes coloration differencesbetween males and females2To answer question 1 Hill found that the color of female population is difference based on which locality the birds are from This was due to the amount of carotenoid containing food that was available in the areaFor question 2 males are always looking for carotenoid based food than females that is why their plumage is much brighterThis leads to an ultimate question about why do females not seek for carotenoidrich food The answer simply being that they do not benefit from bright plumage like males do and only care for calorie intakeIn his experiment Hill found out that the brighter the plumage of a male the higher their chances of finding a mate But why was thisThe female finches chose bright colored males for three reasonsBrighte
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